在河道狭窄的重要堤段，常采用（）。
A.坡式护岸
B.坝式护岸
C.墙式护岸
D.平顺护岸
参考答案：C
Never before _____seen anybody who can play tennis as well as Robert.
A．had she
B．she had
C．has she
D．she has
压力容器使用中易产生的缺陷有（）
A.漏气
B.腐蚀
C.裂纹
D.变形
